The Voyager-Kazon conflict was a two-year period from 2371-2373 during which the USS Voyager was attacked multiple times by the Kazon-Nistrim sect, although other sects were involved to a degree. The conflict began after Voyager destroyed the Caretaker's array shortly after Voyager's arrival in the Delta Quadrant, denying the Kazon its advanced technology.
By 2371, the Caretaker had been pulling in ships from all over the galaxy hoping to find a suitable mate so his offspring could take over his role of caring for the Ocampan people following his death. Two vessels that had recently been pulled into the region were the Federation starship USS Voyager, commanded by Captain Kathryn Janeway, and the Maquis raider Val Jean, commanded by Chakotay. Following his genetic testing on the Voyager and Val Jean crew, he sent two of their crewmembers to the Ocampan homeworld to be treated for an illness contracted during the testing.
While searching for their missing crewmembers, the Val Jean and Voyager came across a Talaxian by the name of Neelix. He offered to assist the crews find their missing people in exchange for water to pay back to the Kazon-Ogla. When the two crews and Neelix beamed down to the barren Ocampan surface, they were taken by the Kazon and spoke to their maje, Jabin. Although Captain Janeway appeared to be making progress in negotiating with Jabin, Neelix proceeded to take him hostage; he then took his girlfriend, Kes, and fired his phaser at the water containers beamed down by Voyager, allowing them to escape while the Kazon were distracted.
After the missing crewmembers were recovered, Voyager and the Val Jean proceeded to the Caretaker's array to negotiate passage back to the Alpha Quadrant. By the time they arrived, multiple Kazon ships were already arriving at the array to investigate the entity's "strange behavior." With no intention of allowing anyone to beam over to the array, the Kazon attacked Voyager and the Val Jean. During the battle, a large Kazon carrier vessel arrived and began inflicting serious damage to Voyager. Chakotay had his crew transported to Voyager with the intention of "taking some heat" off the vessel's tail. Chakotay rammed the Val Jean into the Kazon vessel, beaming out a split second before the impact that destroyed his ship and crippled the large Kazon starship.
Meanwhile, on board the array, the Caretaker himself was near death. He attempted to activate a self-destruct sequence, but the damaged Kazon carrier vessel collided with the array, severely damaging the station and rendering the self-destruct sequence inactive. His final words before his death were to Captain Janeway, who had managed to beam over with Lieutenant Tuvok, stating that the installation must be destroyed to prevent the Kazon from using the technology to harm the Ocampa. Although Tuvok believed that destroying the array would violate the Prime Directive, Janeway reasoned that the Voyager crew was "already involved" in the situation and made the decision to destroy the array.
Upon returning to Voyager, Janeway had Tuvok arm the tricobalt devices necessary to destroy the array. Voyager fired two devices at a yield of 20,000 teracochranes, obliterating the array and leaving no debris. Jabin hailed Voyager immediately afterward, informing Janeway that she had made an enemy that day. The remaining Kazon ships then immediately withdrew. (VOY: "Caretaker", "The Voyager Conspiracy")
Seska defects to the Nistrim
Upon the destruction of the Val Jean, the Maquis crew were invited to join the crew of Voyager for the seventy-year journey home. One of these crewmembers, Seska, joined as an ensign in the engineering department. Unknown to the Voyager crew, Seska was actually a Cardassian spy assigned to infiltrate Chakotay's crew and report on Maquis activities, just as Tuvok was for the Federation. Unfortunately, Seska strongly disagreed with Captain Janeway's decision to destroy the array, and began secret negotiations with the Kazon-Nistrim. Her first act was to deliver a replicator to the Kazon, although their lack of knowledge about the technology caused severe damage to one of their ships and the deaths of the crew. When Voyager found the replicator, the crew suspected that someone had given the technology to the Kazon, and an investigation exposed Seska. Upon her discovery, Seska spoke of her dislike for Janeway and her decision to strand Voyager in the Delta Quadrant. She then immediately beamed to a nearby Kazon vessel and disappeared. (VOY: "State of Flux")
Frequent attacks and treason
With Seska supplying information about Voyager and training them in Cardassian battle tactics, the Kazon were able to raid Voyager and steal a transporter module in 2372. Although Commander Chakotay was able to destroy the module a brief time later, he was captured and interrogated by the Kazon. Before Voyager was able to rescue him, Seska took a sample of his DNA and impregnated herself with it. (VOY: "Maneuvers")
A later Kazon attack, the fourth in a two-week period of time, took the life of a former Maquis, Kurt Bendera, who was popular with many of the Maquis on board including Chakotay, B'Elanna Torres, and Ensign Hogan. Feeling that Starfleet's policies were not working with the Kazon, Chakotay suggested a new approach: making a deal. A summit was arranged to discuss the possibility of an alliance with some of the Kazon sects. Voyager would offer to defend any allied ships from attack and provide emergency aid to ships and outposts in exchange for the cessation of hostilities. Unfortunately, the talks were cut short by an attack by the Trabe, the race who had formerly oppressed the Kazon. The Trabe had hoped to wipe out the Kazon leadership and throw the sects into chaos, but was stopped by Voyager. Unfortunately hostilities between the vessel and the Kazon continued. (VOY: "Alliances")
Sometime in 2372, Michael Jonas began feeding information about Voyager to the Kazon. Although Lieutenant Tuvok was able to detect that someone had contacted the Nistrim, he was unable to pinpoint who it was and where it was coming from. A plan was concocted between himself, Captain Janeway, and Lieutenant Tom Paris to have Paris start behaving like a malcontent in order to make the impression that he wanted to leave the ship. The plan was successful, with Paris getting into fights with both Chakotay and Lieutenant Rollins to curb any suspicion of his true intentions. Upon leaving Voyager, Paris was captured by the Kazon as planned. After examining the Kazon computer, he discovered Michael Jonas' treason and quickly made his escape back to Voyager with the news. Meanwhile, back on Voyager Neelix had discovered Jonas' betrayal by his own methods, and was able to kill him during a fight in engineering. (VOY: "Dreadnought", "Lifesigns", "Investigations")
By the end of 2372, Seska had given birth to her child. She contacted Voyager and pleaded desperately for help as Maje Culluh had realized that the child was not his and planned on raising him to be a slave. Although realizing the possibility of Kazon deception, the Voyager crew rallied behind Chakotay and his responsibility to his son. Holographic projectors were installed on Voyager's hull to give the illusion of friendly ships to draw enemy fire away from Voyager, and the ship was within close range of a Talaxian colony willing to provide aid in the event of an ambush. Unfortunately, despite the crew's best efforts, Voyager was captured by Kazon forces in the ensuing ambush. Lieutenant Tom Paris managed to escape the combat zone in a shuttle and went back to the Talaxian colony to get help, but not before the Voyager crew was marooned on Hanon IV.
On Voyager, The Doctor and Lon Suder, a recovering sociopathic Betazoid, remained on board. The Doctor was tied into the sickbay systems at the time and unable to join the crew on Hanon, and Suder had successfully remained hidden during the Kazon attack. Together they managed to sabotage Voyager's backup phaser couplings as well as other systems on board. The Doctor also uncovered that Seska's child was in fact Culluh's and not Chakotay's.
Paris and the Talaxian fleet managed to intercept Voyager and disable the vessel, with The Doctor and Suder's sabotage playing a key role in securing the vessel. Seska and Suder were killed during the final battle, but Culluh (with his son) and several Kazon soldiers escaped Voyager in escape pods. Paris then proceeded to pick up the Voyager crew on Hanon IV. (VOY: "Basics, Part I", "Basics, Part II")
Voyager left Kazon space in early 2373 following Voyager's recapture. Given the immense distance between the Federation and the Kazon Collective, the repercussions for the Kazon following the conflict with Voyager may never be known. Voyager herself suffered heavy damage at the hands of the Kazon during the conflict, and lost at least half a dozen crewmembers. Fortunately, the damage done to Voyager did not hinder its ability to return to the Alpha Quadrant in 2378.